Kidneys:
As a mammal, manatees need fresh water. But how do they find it? They
can find fresh water by swimming inland to freshwater rivers or canals,
or places where freshwater runs from drainage sources. Sometimes, in
order to obtain freshwater, manatees will siphon freshwater that is
floating atop saltwater, such as rain water that has fallen.

Have you
ever swam in a ocean and accidentally swallowed saltwater? How did it
make you feel? Did you know that if you drank just a half glass of saltwater,
you'd likely vomit--a good thing because it would protect your body
from the life-threatening dangers of too much salt.

Because
Manatee spend their time in both fresh and saltwater habitat, manatees
certainly do take in saltwater, such as when they are eating the saltwater
plants. So how do the manatees handle the salt water that they take
in?

The answer is in their kidneys. Manatees kidneys are able to filter
blood to control levels of salt and to maintain water balance. According
to Cathy Beck of the Sirenia Project, the anatomy of the manatee kidney
and how it has evolved to accommodate this switch between saline and
fresh water environments has been studied, most notably by Dr. Noble
Maluf, an anatomist in Cleveland, Ohio. He found the kidney of the manatee
is fundamentally different from that of the dugong, a strictly marine
(saltwater)sirenian. When in salt water, the manatee kidney has an astounding
ability to concentrate the urine (i.e. retain fresh water) to at least
1,160 mosM/liter (seawater is 1,000 mosM/liter).